A Johns Hopkins study finds that people who have a
family history of heart disease have more reason than most
to keep their weight down. In these families, the research
team found that siblings who were obese or overweight had a
60 percent increased risk of suffering a serious heart
ailment, such as a heart attack, before the age of 60.

The study, published in the journal Circulation
online April 19, is believed to be the first measure of
additional risk from increased body mass index in such
populations. (BMI equals weight in kilograms per height in
square meters.) People are considered to be obese when
their BMI is greater than or equal to 30 kilograms per
meter squared; overweight is defined as a BMI of 25 to 29.9
kilograms per meter squared. For example, someone who is 5
feet, 10 inches tall who weighs 250 pounds has a BMI of 41
kilograms per meter squared.

"There is a growing epidemic of obesity among
Americans, with two-thirds of Americans overweight," said
senior investigator Diane Becker, a professor at the
schools of Medicine and Public Health. "Because overweight
and obesity are risk factors for heart disease, physicians
and the public should know what additional risk applies for
siblings in families with known heart problems so that
appropriate monitoring and therapy can be performed."

The study's results highlight the importance of BMI in
assessing overall risk to heart health and supplement
traditional risk assessments, such as the Framingham Risk
Score, the researchers said. Traditional FRS scoring
measures the likelihood of developing major heart problems,
such as a heart attack, within 10 years. However, the FRS
score, originally developed in the 1990s, omits BMI, taking
into account traditional leading risk factors for heart
disease, such as age, gender, cholesterol levels, blood
pressure, smoking and diabetes.

In the Johns Hopkins study, researchers monitored for
nine years risk factors, both traditional and BMI, in 827
siblings under age 60 from families in the Baltimore
region. Study participants were generally healthy at the
beginning of the study, with no early signs of heart
disease, but all had at least one major risk factor. Every
participant also had at least one sibling with premature
coronary heart disease (such as blocked arteries) that had
required hospitalization, so family history was a risk
factor. Half the participants were women, 20 percent were
black Americans, and the rest were predominantly white.
Blood tests and physical exams were conducted at the
beginning and end of the study to assess changes in each
individual's risk factors.

Results showed that 13.3 percent of siblings had a
premature incident of heart disease within a nine-year
period. Of these, obese and overweight siblings had
similarly higher incident rates of 15.3 percent and 16
percent, respectively, double the rate in siblings with a
normal weight. According to Becker, this translates into a
4 percent increase in risk of coronary heart disease for
every one-unit increase in BMI.

Indeed, obesity was found to have the greatest impact
on risk of heart disease in siblings who had multiple risk
factors that gave them a high FRS score. In this group with
a high FRS score, obese siblings had twice the amount of
coronary heart disease as those who were overweight--40
percent and 20 percent, respectively--and double the rate
in siblings with normal-weight siblings. When compared to
siblings with low FRS scores and normal weight, obese
siblings with high FRS scores had 15 times more premature
heart disease.

When genetic traits were analyzed, the Johns Hopkins
team found that 50 percent of BMI in whites was hereditary,
while in blacks, the hereditary factor was even less, at 30
percent. This means that lifestyle and environmental
factors account for the rest, the researchers said,
suggesting that much of BMI is not associated with family
history and, as a result, it can be changed and
improved.

"Our results show that obesity is far more important
than previously thought to gauging real risk of heart
disease in families where this is already a problem," said
the study's lead author, cardiologist Samia Mora, then a
research fellow at Johns Hopkins. "When monitoring these
patients with traditional Framingham Risk Scores,
physicians should also closely monitor body mass index,
even when it is mildly elevated, and incorporate weight
reduction programs into treatment plans accordingly. These
siblings really need to watch their weight. Fortunately, it
is a risk factor that can be modified."

Results from the study could not fully explain the
strong link between obesity and premature heart disease.
Further research is planned to verify its biological and
genetic origins.

The study, which analyzed data collected from 1980 to
1989, was part of a larger long-term study of familial
relationships in heart disease called the Sibling Family
Heart Study. Funding was provided by the National
Institutes of Health and the Johns Hopkins Clinical
Research Center. Other investigators in this research were
Lisa Yanek, Taryn Moy, M. Daniele Fallin and Lewis
Becker.